A forging method for high manganese, high chromium and high nitrogen austenitic steel

Abstract

The present invention provides a forging method for high-manganese, high-chromium, high-nitrogen austenitic steel. This method utilizes a press and a radial precision forging machine to alter the material deformation mode and control the metal's plastic deformation process to produce high-quality forgings. The forging method comprises the following steps: 1) heating; 2) rounding; 3) upsetting; 4) drawing; 5) heating; 6) finish forging; and 7) air cooling. The present invention utilizes a simple process flow. The slow upsetting followed by full rounding not only enhances plastic deformation and reduces the risk of cracking, but also prevents rapid heating of the core of the billet during upsetting, effectively breaking up the original billet's as-cast structure and welding away defects such as pores and looseness. Drawing, performed using the LZ forging method, ensures compaction, resulting in forgings with good forgeability and effectively preventing material deviation. Furthermore, temperature and forging control techniques are employed during precision forging to achieve a uniform structure and fine grain size while ensuring compaction, thereby enhancing material properties.

Description

Technical Field

[0001] The invention belongs to the technical field of metal plastic forming and relates to a forging method for high-manganese, high-chromium and high-nitrogen austenitic steel. Background Art

[0002] High manganese, high chromium, high nitrogen austenitic steel is a type of steel developed through microalloying on the basis of high manganese steel. It has good wear resistance, toughness, low temperature resistance, corrosion resistance, and non-magnetic properties, and has been widely used in shipbuilding, construction, transportation, electrical, machinery and other industries.

[0003] Because this steel is difficult to heat-work, forging is extremely challenging and prone to cracking during forging, high-manganese, high-chromium, high-nitrogen austenitic steel is currently mostly cast. In recent years, with the continuous improvement of my country's steel manufacturing technology and the gradual transformation and upgrading to high-end production, a forging method suitable for industrial production is urgently needed to improve internal structure, product quality, and service life. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a forging method for high manganese, high chromium, high nitrogen austenitic steel by using a press and a radial precision forging machine to change the material deformation mode and control the metal plastic deformation process to produce high-quality forgings.

[0005] The technical solution of the present invention is achieved as follows: a forging method for high manganese, high chromium and high nitrogen austenitic steel, the forging comprising the following steps:

[0006] Step 1) Heating: Load the blank into a heating furnace and heat it to a temperature of 1000°C to 1200°C through a three-stage heating method. The holding time is not less than 8 hours to achieve plastic forging.

[0007] Step 2) Rolling: Roll the whole body into a round shape, pressing down 10 to 60 mm;

[0008] Step 3) Upsetting: Slowly upsetting the steel with the ingot guard on the press to ensure that the height-to-diameter ratio after upsetting is between 0.68 and 0.85, and the upsetting coefficient does not exceed 2.5. In addition, pause for a few seconds during the upsetting process.

[0009] Step 4) Lengthening: Square the ingot on the upper and lower flat anvils, turn the ingot into eight sides, and keep the reduction rate at 10% to 20%. Control the anvil width ratio at 0.7 to 0.95 and the material width ratio at 0.70 to 1.2. Remove the ingot guard plate and level the ingot tail end surface.

[0010] Step 5) Heating: Return to the heating furnace, furnace temperature 950℃~1050℃, holding time 1~3 hours;

[0011] Step 6) Fine forging: Use a radial fine forging machine with a rectangular hammer head forging. When forging with the fine forging machine, control the hammer depth per pass to no more than 70mm, and the finishing pass pulling speed to no more than 3m / min. Water spraying is prohibited during the entire forging process. In the last two passes, leave 3-10mm in width and height for finishing.

[0012] Step 7) Air cooling: After air cooling to room temperature, the high manganese, high chromium, and high nitrogen austenitic steel forging process is completed.

[0013] The blank of the high manganese, high chromium and high nitrogen austenitic steel is an electroslag ingot.

[0014] The forged product of the high manganese, high chromium and high nitrogen austenitic steel is a square piece.

[0015] The process of blanking high manganese, high chromium and high nitrogen austenitic steel press is divided into three steps: first, the whole body is rounded, then it is upset with the ingot guard plate, and finally it is stretched.

[0016] The LZ forging method is used in the drawing process of high manganese, high chromium and high nitrogen austenitic steel press. The square drawing is carried out on the upper and lower flat anvils. The reduction rate is 10% to 20%, the anvil width ratio is controlled in the range of 0.7 to 0.95, and the material width ratio is controlled in the range of 0.70 to 1.2.

[0017] In step 6), the initial forging temperature of the high manganese, high chromium, high nitrogen austenitic steel during the precision forging stage is 1050-900°C, and the final forging temperature is not less than 800°C.

[0018] In step 6), a special rectangular hammer is used for precision forging of high manganese, high chromium, and high nitrogen austenitic steel. Water spraying is prohibited during the entire forging process. There are two finishing passes at the end of the forming. In the first finishing pass, 3 to 10 mm is left on the wide and narrow sides for finishing; the second finishing pass is done without leaving any amount.

[0019] The positive effects of the present invention are as follows: the process flow is simple. By rolling the entire billet and then slowly upsetting it, not only can plastic deformation be improved and the risk of cracking be reduced, but also rapid heating of the core of the billet during the upsetting process can be avoided, the as-cast structure of the original billet can be fully broken up, and original structural defects such as pores and looseness can be welded together. The LZ forging method is used for elongation, which ensures the compaction effect, makes the forging have good forgeability, and effectively prevents material deviation. In addition, by adopting temperature and forging control technology during precision forging, a uniform structure and fine grain size are obtained while ensuring the compaction effect, thereby improving material properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the finished forging product of high manganese, high chromium and high nitrogen austenitic steel forgings.

[0021] 1. M2 manipulator; 2. Square forgings; 3. Rectangular special hammer head for radial precision forging machine; 4. M1 manipulator. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described below with specific embodiments:

[0023] Example 1: The electroslag ingot used in this example weighs 2.6 tons and is made of 70Mn18Cr7N. The forging process of high manganese, high chromium, and high nitrogen austenitic steel is as follows:

[0024] Step 1) Heating: Place the electroslag ingot into a heating furnace and heat it to 1180°C through a three-stage heating method. Keep the temperature for 10 hours to achieve plastic forging.

[0025] Step 2) Rolling: Roll the whole body into a round shape, pressing down 10 to 60 mm;

[0026] Step 3) Upsetting: Upsetting: Slowly upsetting with the ingot guard on the press until the height is 650mm (diameter is Φ810mm), pausing for 6 seconds during the upsetting process;

[0027] Step 4) Drawing length: Use LZ forging method to draw length to 380mm on upper and lower flat anvils, control the reduction rate at 10% to 20%, the anvil width ratio at 0.7 to 0.95, the material width ratio at 0.70 to 1.2, and heat the eight sides to 400mm; remove the ingot guard plate and level the ingot tail end surface;

[0028] Step 5) Heating: Return to the heating furnace, furnace temperature 1000℃, holding time 3 hours;

[0029] Step 6) Precision forging: Water spraying is prohibited throughout the process. A radial precision forging machine with a rectangular special hammer head 3 is used to forge the finished product into a square forging 2 measuring 213×315mm. During forging, the hammer depth per pass is controlled to be no more than 70mm, and the finishing pass drawing speed is no more than 3m / min. 1 is the M2 manipulator, and 4 is the M1 manipulator. The initial forging temperature of the high manganese, high chromium, and high nitrogen austenitic steel during the precision forging stage is 1050-900°C, and the final forging temperature is not less than 800°C.

[0030] A special rectangular hammer is used for precision forging of high manganese, high chromium and high nitrogen austenitic steel. Water spraying is prohibited during the entire forging process. There are two finishing passes at the end of the forming process. In the first finishing pass, 3 to 10 mm is left on the wide and narrow sides for finishing; the second pass is a finishing pass without leaving any amount.

[0031] Step 7) Air cooling: After air cooling to room temperature, the high manganese, high chromium, and high nitrogen austenitic steel forging process is completed.

Claims

1. A forging method for high manganese, high chromium, high nitrogen austenitic steel, characterized in that: Forging includes the following steps: Step 1) Heating: Load the blank into a heating furnace and heat it to a temperature of 1000°C to 1200°C through a three-stage heating method. The holding time is not less than 8 hours to achieve plastic forging. Step 2) Rolling: Roll the whole body into a round shape, pressing down 10 to 60 mm; Step 3) Upsetting: Slowly upsetting the steel with the ingot guard on the press to ensure that the height-to-diameter ratio after upsetting is between 0.68 and 0.85, and the upsetting coefficient does not exceed 2.

5. In addition, pause in the middle of the upsetting process; Step 4) Drawing: The high manganese, high chromium, high nitrogen austenitic steel press drawing process adopts LZ forging method, and the drawing is carried out on the upper and lower flat anvils, and the eight sides are turned. The pressing rate is 10% to 20%, the anvil width ratio is controlled in the range of 0.7 to 0.95, and the material width ratio is controlled in the range of 0.70 to 1.2; the ingot guard plate is staggered and the ingot tail end surface is flat; Step 5) Heating: Return to the heating furnace, furnace temperature 950℃~1050℃, holding time 1~3 hours; Step 6), precision forging: using a radial precision forging machine with a rectangular hammer head forging, the amount of hammer dropped per pass is controlled to be no more than 70mm during the precision forging process, the pulling speed of the finishing pass is no more than 3m / min, water spraying is prohibited during the entire forging process, and the width and height are left 3-10mm for finishing in the last two passes; wherein, the initial forging temperature of the precision forging forming stage of high manganese, high chromium, high nitrogen austenitic steel is 1050-900℃, and the final forging temperature is not less than 800℃; a special rectangular hammer head is used for precision forging of high manganese, high chromium, high nitrogen austenitic steel, and there are two finishing passes at the end of the forming process. In the first finishing pass, 3-10mm is left on the wide and narrow sides for finishing; the second pass is not left for finishing; Step 7) Air cooling: After air cooling to room temperature, the high manganese, high chromium, and high nitrogen austenitic steel forging process is completed.

2. The forging method of high manganese, high chromium, high nitrogen austenitic steel according to claim 1, characterized in that: The blank of the high manganese, high chromium and high nitrogen austenitic steel is an electroslag ingot.

3. The forging method of high manganese, high chromium, high nitrogen austenitic steel according to claim 1, characterized in that: The forged product of the high manganese, high chromium and high nitrogen austenitic steel is a square piece.

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